Added ObjectCollection::toKeyIndex($keyColumn).
Added test for ObjectCollection:toKeyIndex() method.
Fixed table/column renaming bug in migration process.

If the migration process decides to rename a table or a column it needs to make sure that it does not rename multiple tables or columns to the same name. Thus I've implemented a `$renamed` array that tracks each renaming so we don't have a duplicated renaming.
Merge pull request #398 from marcj/fix-migration

Fixed table/column renaming bug in migration process.
Merge pull request #391 from marcj/main-master

Added ObjectCollection::toKeyIndex($keyColumn).
added missing fail() assertions to make test fail when exception get accidently droped. fixes #364.
Fix CS
added __METHOD__ for exception messages, where method names are mentioned. fixed phpdocs. closes #353.